We have proposed a study of the relationship of the renin-angiotensin system and the kallikrein-kinin system by utilizing the low levels of angiotensin and kinin peptides into the autoperfused rad kidney. We have determined that in this system urinary kallikrein may be related to GFR, and perhaps inversely to urinary K ion. We also have determined that infusions of angiotensin I results in a decrease in urinary kallikrein. We will in the coming year continue the infusion studies of small quantities of angiotensin I after a converting enzyme inhibitor, angiotensin II (with and without a competitive inhibitor) tetradecapeptide renin substrate, bradykinin and kallikrein which we are presently purifying in our laboratory. In these experiments urinary and renal kallikrein will be measured as will mean arterial pressure, GFR, RBF, urinary Na ion, K ion and osmolality. These experiments should lead to a better understanding of the interrelationship of the peptide systems, and also to a better understanding of factors which control or influence kallikrein.